Overview
Its belly lies lateral to the extensor carpi radialis. In cattle it has two bellies, each with its own tendon, crossing the dorsal surface of the carpus and metacarpus:
- Medial belly: the proper extensor of digit III (m. extensor digiti III proprius), also called the medial digital extensor. It ends on the medial digit (III).
- Lateral belly: the common digital extensor proper. Its tendon splits at the distal end of the metacarpus into two branches, one for each main digit (III and IV).
The lateral digit (IV) also has its own extensor, the lateral digital extensor, which is not part of this muscle.
Origin
Lateral epicondyle of the humerus.
Insertion
- Medial belly: middle phalanx of digit III.
- Lateral belly: extensor processes of the distal phalanges of digits III and IV.
Action
Extends the digital joints and the carpus.
Innervation
Radial nerve (n. radialis).
Clinical relevance
With radial nerve paralysis the animal cannot extend its digits: it knuckles over onto the dorsal surface of the hoof and drags it as the limb advances.